Hi all, My first post. I read back through quite a few posts on here with interest. Have sortof a technical question about the delivered product.

Q: Is there an FAQ that addresses file formats (like mp3, wav, other?), file resolution, and structure of audio files - especially loops - that are generally used in games? Do you supply several different components of a loop that the game engine integrates (sparse / medium/dense / action/ calm mix etc), or is it more generally a finished singular composition? something in between?

Appreciate any responses. Really I'm just trying to understand the necessary technical standards that audio needs to meet from a formating and deliverable perspective to easily integrate with the finished product.

Mp3 or ogg-vorbis are often used for music.
Wav is often used for sound effects.
The bit resolution depends on the qualtity, from 8 bit, to more common 16 bit interger to float.
The frequency is often 40/48khz up to 96khz or higher, eventually it depends on the performance and hardware support, but sound APIs will support most of them.

Raw sound data from a library should have the highest quality, the sound engineer of the game will reduce the bit depth/frequency to meet the game requirements !

In games you have something from simple playback (playback a mp3 as background, add some interactive sound effects) up to an interactive, situation dependent,adaptive on-the-fly music composition (several channels are mixed on-the-fly).

I'd advise against using mp3 whenever you can use the Ogg Vorbis file format instead.
Mp3s are a real hassle to loop properly without them causing little snaps & pops due to sampling overlaps, the audio quality / file size ratio isn't as good and to top it off, the dev will have to buy a license to use the codec in the game at some point.
I usually hand over both uncompressed PCM (.wav/.aiff) and compressed (mostly .ogg) in a neat "Final" folder structure.
Amounts of compression, sample & bit rate really depend on what's needed - or rather on what's provided and how much space you've got left. You'll just have to see from situation to situation. In most cases, 44.1 kHz @ 16 bit resolution is quite enough, though!
As a crass counter-example: the Wiimote only plays back 4-bit (!) PCM, mostly at 3000 Hz samplerate.

Regarding if you send over a finished track or different instruments: that really depends, too.
If the music will never be taken apart anyway, and it's a mobile game where file size is an issue, I definitely prefer handing over the complete thing 'cause then I have the mix in my own hands.

Wanted to thank both for the replies on this. It helps alot to have this info - at least for me. I didn't realize ogg would be that widely used.

I was curious about the individual tracks vs. premixed tracks partially due to thinking about licensing of loops. My understanding is that royalty free loops (big fish and sony is what I have now and I make my own) but the licensing on the royalty free stuff means I have to change them to use them. Didn't know if there were concerns about unmixed loops used in games (as individual seperate tracks)- even if the final product is ultimately a mix that comes out of the speakers as a mix. Anybody had concerns / issues with that? I'm a total Noob - mostly a songwriter who likes organic instrumental stuff - and the licensing problems it seems you might get into can seem scary unless I do 100% my own loops / samples / sounds / recordings / etc.

"Normal" audio is typically 44100Hz, 16-bit, lossy compressed (either with MP3, Vorbis, or AAC) with a data rate of ~192kbps, though the data rate frequently ranges from 128kbps to 320kbps.

Go with Vorbis if you can. The legal complexities are simpler, it offers great quality, and as Moritz P.G. Katz points out, it can properly loop (MP3s have a delay padding at the beginning and ending of the audio, so when you loop there's a noticeable gap, so it takes some extra work on your part to gaplessly loop them).